I've used Crystal Ball since Oct last year and when I saw a FB post for the AppSumo deal I grabbed it.

I manage a number of different websites for my business and my clients -- including eCommerce, business/informational, and educational sites. Remembering what impacted traffic to those sites is tough -- was it a holiday, event, ad promotions, etc.

Crystal Ball has greatly simplified this because I can add annotations on each property's Google Analytics charts to see of what happened when.

I love that I can add annotations directly using their Chrome Extension without logging into my account. I can annotate on the fly and it appears on my Analytics chart like a helpful sticky note reminder.